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| United States Patent |
6,203,205
|
|
Murai
, et al.
|
March 20, 2001
|
Cylindrical roller bearing
Abstract
A cylindrical roller bearing comprises an inner race, an outer race, a
plurality of cylindrical rollers disposed between the inner race and the
outer race, and a cage disposed between the inner race and the outer race
and provided with pocket portions in which the plurality of cylindrical
rollers are respectively accommodated. The cylindrical roller bearing
satisfies a following relations
1.5.times.10.sup.-3 D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D
and
A/B=0.6.about.1.0
where D is a diameter of a cage circumferential surface of the cage which
is either one of inner and outer circumferential surfaces of an axial end
portion of the cage, H is a size of an annular clearance between the cage
circumferential surface and a race circumferential surface which is either
one of an outer race rib inner-diameter surface and an inner race rib
outer-diameter surface opposite to the cage circumferential surface, A is
an axial length of the cage circumferential surface and B is an axial
length of the race circumferential surface. The bearing using a system for
guiding the cage a roller guide system in which radial displacement of the
cage is limited by engagement between each pocket and a corresponding
roller. A roller guide surface of the cage is provided in a portion
opposite to a linear-form portion at least except crowning portions in an
axial direction of a roller rolling surface.
| Inventors:
|
Murai; Takashi (Kanagawa, JP);
Yamamoto; Takashi (Kanagawa, JP);
Tsunashima; Shinichi (Kanagawa, JP)
|
| Assignee:
|
NSK Ltd. (Tokyo, JP)
|
| Appl. No.:
|
351327 |
| Filed:
|
July 12, 1999 |
Foreign Application Priority Data
| Jul 10, 1998[JP] | 10-195890 |
| Current U.S. Class: |
384/450; 384/470; 384/523; 384/572 |
| Intern'l Class: |
F16C 033/46; F16C 033/38; F16C 033/66 |
| Field of Search: |
384/470,523-534,572-580,450
|
References Cited
U.S. Patent Documents
| 5716146 | Feb., 1998 | Murai et al. | 384/450.
|
| Foreign Patent Documents |
| 3-67718 | Jul., 1991 | JP.
| |
Primary Examiner: Hannon; Thomas R.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas, PLLC
Claims
What is claimed is:
1. A cylindrical roller bearing comprising:
an inner race;
an outer race;
a plurality of cylindrical rollers disposed between said inner race and
said outer race; and
a cage disposed between said inner race and said outer race and provided
with pocket portions in which said plurality of cylindrical rollers are
respectively accommodated,
wherein said cylindrical roller bearing satisfies a following relations
1.5.times.10.sup.-3 D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D
and
A/B=0.6.about.1.0
where
D is a diameter of a cage circumferential surface of said cage which is
either one of inner and outer circumferential surfaces of an axial end
portion of said cage,
H is a size of an annular clearance between said cage circumferential
surface and a race circumferential surface which is either one of an outer
race rib inner-diameter surface and an inner race rib outer-diameter
surface opposite to said cage circumferential surface,
A is an axial length of said cage circumferential surface and
B is an axial length of said race circumferential surface,
wherein a roller guide surface of said cage is provided in a portion
opposite to a linear-form portion at least except crowning portions in an
axial direction of a roller rolling surface.
2. The cylindrical roller bearing according to claim 1, wherein said
bearing uses a roller guide system in which radial displacement of said
cage is limited by engagement between each pocket and a corresponding
roller.
3. The cylindrical roller bearing according to claim 1, wherein said
clearance size H satisfies a following equation
4.5.times.10.sup.-3 D.ltoreq.H.ltoreq.7.5.times.10.sup.-3 D.
4. A cylindrical roller bearing comprising:
an inner race;
an outer race having ribs at both ends in an axial direction of said roller
bearing and having a roller rolling surface between said ribs, said roller
rolling surface including crowning portions and a linear-from portion
interposed between said crowning portions;
a plurality of cylindrical rollers disposed between said inner race and
said outer race; and
a cage disposed between said inner race and said outer race and provided
with pocket portions in which said plurality of cylindrical rollers are
respectively accommodated, said cage having a roller guide surface which
is provided in a portion opposite to said linear-form portion at least
except crowning portions in an axial direction of said roller rolling
surface,
wherein said cylindrical roller bearing satisfies a following relations
1.5.times.10.sup.-3 D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D
and
A/B=0.6-1.0
where
D is a diameter of an outer circumferential surface of an axial end portion
of said cage,
H is a size of an annular clearance between said outer circumferential
surface of said cage and an outer race rib inner-diameter surface of said
rib which is opposite to said outer circumferential surface of said cage,
A is an axial length of said outer circumferential surface of said cage and
B is an axial length of said outer race rib inner-diameter surface.
5. The cylindrical roller bearing according to claim 4, wherein said
clearance size H satisfies a following equation
4.5.times.10.sup.-3 D.ltoreq.H.ltoreq.7.5.times.10.sup.-3 D.
6. A cylindrical roller bearing comprising:
an outer race;
an inner race having ribs at both ends in an axial direction of said roller
bearing and having a roller rolling surface between said ribs, said roller
rolling surface including crowning portions and a liner-from portion
interposed between said crowning portions;
a plurality of cylindrical rollers disposed between said inner race and
said outer race; and
a cage disposed between said inner race and said outer race and provided
with pocket portions in which said plurality of cylindrical rollers are
respectively accommodated, said cage having a roller guide surface which
is provided in a portion opposite to said linear-form portion at least
except crowning portions in an axial direction of said roller rolling
surface, wherein said cylindrical roller bearing satisfies a
following relations
1.5.times.10.sup.-3 D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D
and
A/D=0.6-1.0
where
D is a diameter of an inner circumferential surface of an axial end portion
of said cage,
H is a size of an annular clearance between said inner circumferential
surface of said cage and an inner race rib outer-diameter surface of said
rib which is opposite to said inner circumferential surface of said cage,
A is an axial length of said inner circumferential surface of said cage and
B is an axial length of said inner race rib outer-diameter surface.
7. The cylindrical roller bearing according to claim 6, wherein said
clearance size H satisfies a following equation
4.5.times.10.sup.-3 D.ltoreq.H.ltoreq.7.5.times.10.sup.-3 D.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical roller bearing incorporated
in a general machine such as a middle-size electric motor, a large-size
electric motor, or the like, and particularly to a cylindrical roller
bearing in need of low vibration and low noise.
As a vibration/noise reducing technique for a cylindrical roller bearing,
for example, as shown in Japanese Utility Model Unexamined Publication No.
Hei. 3-67718, there is known a technique in which a roller guide system is
used as a system for guiding a cage so that the weight of the cage is
loaded on rollers which are existed within unloading-zone (hereinafter
refering unloading-zone rollers). The load of the weight of the cage is
set against centrifugal force acting on rolling rollers so that the
pressure of contact of rollers with an outer race is reduced. As a result,
the motion of the unloading-zone rollers is restricted so that reduction
of vibration/noise of the bearing is attained.
In a pressed cage for low vibration and low noise, generally, a roller
guide surface d of a cage a is formed so as to be opposite to a crowning
portion e of a roller rolling surface as shown in FIG. 7.
In the bearing vibration/noise reducing technique disclosed in Japanese
Utility Model Unexamined Publication No. Hei. 3-67718, however, as shown
in FIG. 8, the pitch circle diameter of pocket holes b of a cage a was set
to be smaller than the pitch circle diameter of rollers c. Accordingly, if
the bearing was produced with an improper difference between the pitch
circle diameters, the restriction in the unloading zone by the cage a
became intense. As a result, the rollers c interfered with the cage a
superfluously. There was a disadvantage that impact noise (cage noise) was
produced due to collision of the rollers c with the cage a.
Further, when the restriction by the cage a was intense, the bearing was
apt to be affected by error in production of individual cages.
Accordingly, vibration and noise levels of the bearing often scattered.
Furthermore, since the guide system was limited to a roller guide system,
the specification of the bearing was limited necessarily.
Further, since the roller guide surfaces d of the cage a were formed in
portions, respectively, opposite to the crowning portions e on the roller
rolling surface as shown in FIG. 7, rollers in the unloading zone in which
the roller motion was limited by being guided by the cage a were made
unstable by the crowning portions so that skew, or the like, occurred
easily. As a result, there was a disadvantage that vibration/noise was
produced in the bearing inclusive of the cage.
Note that an occurrence of this disadvantage is not limited by a type of
guiding system of cage. This disadvantage is generated in a bearing having
a cage of a race guiding system, as well.
The present invention is designed to solve the aforementioned disadvantages
and an object of the present invention is to provide a cylindrical roller
bearing in which not only squeaking noise caused by rubbing of rollers
against inner and outer race surfaces in the unloading zone, cage noise
caused by collision of rollers with the cage and vibration/noise of the
bearing, inclusive of the cage, caused by occurrence of skew, or the like,
can be prevented well but also variations in vibration and noise levels of
individual bearings can be suppressed.
SUMMARY OF THE INVENTION
In order to achieve above object, according to the present invention, there
is provided a cylindrical roller bearing satisfying following
relationships
1.5.times.10.sup.-3 D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D
and
A/B=0.6.about.1.0
where D is a diameter of a cage circumferential surface which is either one
of inner and outer circumferential surfaces of an axial end portion of a
cage, H is a size of an annular clearance between the cage circumferential
surface and a race circumferential surface which is either one of an outer
race rib inner-diameter surface and an inner race rib outer-diameter
surface opposite to the cage circumferential surface, A is an axial length
of the cage circumferential surface and B is an axial length of the race
circumferential surface, wherein a roller guide surface of the cage is
provided in a portion opposite to a linear-form portion at least except
crowning portions in an axial direction of a roller rolling surface.
In the above-mentioned bearing, it is preferable that the bearing uses as a
system for guiding the cage a roller guide system in which a radial
displacement of the cage is limited by engagement between each pocket and
a corresponding roller, or the bearing uses as a system for guiding the
cage a race guide system in which a radial displacement of the cage is
limited by the race.
In the present invention, first, the motion of the rollers existing in the
unloading zone is suppressed through the cage by the damping force of a
lubricant in the annular clearance between the cage circumferential
surface and the race circumferential surface so that squeaking noise
caused by rubbing of rollers against inner and outer race surfaces is
suppressed, the sound pressure level of the cage caused by collision of
rollers with the cage is reduced, and variations in vibration and noise
levels of individual bearings are suppressed.
That is, the size H of the annular clearance between the cage
circumferential surface and the race circumferential surface is restricted
to be in the range of 1.5.times.10.sup.-3
D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D as the relation to the diameter D
of the cage circumferential surface and the ratio of the axial length A of
the cage circumferential surface to the axial length B of the race
circumferential surface is set to be in a range of from 0.6 to 1.0.
Accordingly, the resistance against a flow of the lubricant to pass
through the aforementioned clearance becomes sufficiently intense so that
the cage can be hardly displaced.
As a result, there is no displacement of the cage in accordance with the
motion of rollers even in the case where an irregular motion (revolution
of rollers around their common axis without regular rotation of rollers on
their own axes and radial displacement of rollers) occurs in rollers
existing in the unloading zone.
Further, the cage is controlled by the roller guide system in which the
radial displacement of the cage is limited by engagement between pockets
and rollers. There is a lubricant such as grease, or the like, between the
pockets and the rollers. Since the motion of the cage and the motion of
the rollers restrict each other, the motion of the plurality of rollers
held by the cage is restricted when the clearance size H is limited to
restrict the motion of the cage. As a result, not only the production of
the aforementioned squeaking noise can be suppressed but also the sound
pressure level of cage noise can be reduced. Furthermore, variations in
vibration and noise levels of individual bearings can be suppressed.
Note that, even if the roller guide system of the bearing in which the
radial displacement of the cage is limited by engagement between pockets
and rollers is changed to a race guide system in which a radial
displacement of the cage is limited by the race, the motion of the rollers
held by the cage and the motion of the cage can be controlled as well, to
thereby enjoy the same effects described above. In this case, a
relationship between the peripheral surface of the cage and the peripheral
surface of the race meets a geometrical and positional relationship.
If the clearance size H is smaller than 1.5.times.10.sup.-3 D, a sufficient
amount of the lubricant can be hardly interposed in this clearance. This
causes abnormal abrasion or abnormal temperature rising. If the clearance
size H is larger than 9.0.times.10.sup.-3 D, the resistance against a flow
of the lubricant to pass through the clearance is reduced. As a result,
neither the effect of preventing the production of squeaking noise and
cage noise nor the effect of suppressing variations in vibration and noise
levels of individual bearings can be obtained sufficiently. Incidentally,
when heating at the time of operating the bearing, or the like, is taken
into account, the clearance size H is preferably limited to be in the
range of 4.5.times.10.sup.-3 D.ltoreq.H.ltoreq.7.5.times.10.sup.-3 D.
If A/B is lower than 0.6, the resistance against a flow of the lubricant to
pass through the clearance is reduced. As a result, neither the effect of
preventing the production of squeaking noise and cage noise nor the effect
of suppressing variations in vibration and noise levels of individual
bearings can be obtained sufficiently. If A/B is higher than 1.0, the cage
protrudes from an axial end surface of the outer or inner race and
interferes with other members. This is undesirable in terms of the design
of the bearing.
Further, in the present invention, a roller guide surface of the cage is
provided in at least a portion opposite to a linear form portion except
crowning portions on the axial direction of the roller rolling surface as
well as the aforementioned relations of 1.5.times.10.sup.-3
D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D and A/B=0.6-1.0 are satisfied.
Accordingly, even in the unloading zone in which the roller motion is
guided by the cage so as to be restricted, the rollers are hardly made
unstable so that the occurrence of skew, or the like, can be suppressed
compared with the case where the rollers are guided by portions opposite
to the crowning portions. As a result, vibration/noise of the bearing can
be suppressed.
In addition, the above-mentioned object can also be achieved by a
cylindrical roller bearing according to the present invention comprising:
an inner race;
an outer race having ribs at both ends in an axial direction of the roller
bearing and having a roller rolling surface between the ribs, the roller
rolling surface including crowning portions and a liner-from portion
interposed between the crowning portions;
a plurality of cylindrical rollers disposed between the inner race and the
outer race; and
a cage disposed between the inner race and the outer race and provided with
pocket portions in which the plurality of cylindrical rollers are
respectively accommodated, the cage having a roller guide surface which is
provided in a portion opposite to the linear-form portion at least except
crowning portions in an axial direction of the roller rolling surface,
wherein the cylindrical roller bearing satisfies a following relations
1.5.times.10.sup.-3 D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D
and
A/B=0.6-1.0
where
D is a diameter of an outer circumferential surface of an axial end portion
of the cage,
H is a size of an annular clearance between the outer circumferential
surface of the cage and an outer race rib inner-diameter surface of the
rib which is opposite to the outer circumferential surface of the cage,
A is an axial length of the outer circumferential surface of the cage and
B is an axial length of the outer race rib inner-diameter surface.
Further, the above-mentioned object can also be achieved by a cylindrical
roller bearing according to the present invention comprising:
an outer race;
an inner race having ribs at both ends in an axial direction of the roller
bearing and having a roller rolling surface between the ribs, the roller
rolling surface including crowning portions and a liner-from portion
interposed between the crowning portions;
a plurality of cylindrical rollers disposed between the inner race and the
outer race; and
a cage disposed between the inner race and the outer race and provided with
pocket portions in which the plurality of cylindrical rollers are
respectively accommodated, the cage having a roller guide surface which is
provided in a portion opposite to the linear-form portion at least except
crowning portions in an axial direction of the roller rolling surface,
wherein the cylindrical roller bearing satisfies a following relations
1.5.times.10.sup.-3 D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D
and
A/B=0.6.about.1.0
where
D is a diameter of an inner circumferential surface of an axial end portion
of the cage,
H is a size of an annular clearance between the inner circumferential
surface of the cage and an inner race rib outer-diameter surface of the
rib which is opposite to the inner circumferential surface of the cage,
A is an axial length of the inner circumferential surface of the cage and
B is an axial length of the inner race rib outer-diameter surface.
In the above-mentioned cylindrical roller bearing according to the
invention, it is preferable that the clearance size H satisfies a
following equation, 4.5.times.10.sup.-3
D.ltoreq.H.ltoreq.7.5.times.10.sup.-3 D.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory sectional view for explaining a cylindrical roller
bearing as an embodiment of the present invention;
FIG. 2 is an explanatory sectional view for explaining a cylindrical roller
bearing as a comparative example;
FIG. 3 is a graph showing a result of a rotation acoustic evaluation test;
FIG. 4 is an explanatory sectional view for explaining a cylindrical roller
bearing as another embodiment of the present invention;
FIG. 5 is an explanatory sectional view for explaining the cylindrical
roller bearing as a comparative example in the other embodiment;
FIG. 6 is an explanatory sectional view for explaining a cylindrical roller
bearing as a further embodiment of the present invention;
FIG. 7 is an explanatory sectional view for explaining a conventional
cylindrical roller bearing; and
FIG. 8 is an explanatory view for explaining the conventional cylindrical
roller bearing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred Embodiments of the present invention will be described below with
reference to the drawings.
FIG. 1 is an explanatory sectional view for explaining a cylindrical roller
bearing as an embodiment of the present invention. FIG. 2 is an
explanatory sectional view for explaining a cylindrical roller bearing as
a comparative example. FIG. 3 is a graph showing a result of a rotation
acoustic evaluation test. FIG. 4 is an explanatory sectional view for
explaining a cylindrical roller bearing as another embodiment of the
present invention. FIG. 5 is an explanatory sectional view for explaining
the cylindrical roller bearing as the comparative example in comparison
with the other embodiment. FIG. 6 is an explanatory sectional view for
explaining a cylindrical roller bearing as a further embodiment of the
present invention.
Referring first to FIG. 1, the cylindrical roller bearing 1 is an NU308
type cylindrical roller bearing which satisfies the relations
H=5.0.times.10.sup.-3 D and A/B=0.9 when D is the diameter of a cage
circumferential surface 3 which is an outer circumferential surface of an
axial end portion of a pressed cage 2, H is the size of an annular
clearance existing between the cage circumferential surface 3 and a race
circumferential surface 5 which is an inner-diameter circumferential
surface of an outer race rib 4 opposite to the cage circumferential
surface 3, A is the axial length of the cage circumferential surface 3 and
B is the axial length of the race circumferential surface 5. In the
cylindrical roller bearing 1, as a system for guiding the cage 2, a roller
guide system in which the radial displacement of the cage 2 is limited by
the engagement between each pocket and a corresponding roller 6 is used.
Further, a roller guide surface 7 of the cage 2 is provided in a portion
opposite to a linear form portion 9 except crowning portions 8 on the
axial direction of a roller rolling surface.
Further, a roller dropping preventing portion 10 is provided in an
inner-diameter portion of a substantially axial center portion of the cage
2 to thereby prevent the roller from dropping (decomposing). In this
embodiment, the aforementioned guide surface 7 is provided also in the
roller dropping preventing portion 10. As for the shape of the roller
rolling surface, there is used the roller rolling surface in which a
linear form portion 9 which is 70% of the roller length is left in the
lengthwise center portion of the roller 6 so that crowning portions 8 are
applied to opposite ends, respectively, of the linear form portion 9.
By satisfying the relations H=5.0.times.10.sup.-3 D and A/B=0.9, the
resistance against a flow of the lubricant to pass through the annular
clearance existing between the race circumferential surface 5 and the cage
circumferential surface 3 is made sufficiently large to limit the motion
of the cage 2 to thereby limit the motion of the plurality of rollers 6
because there is a relation that the motion of the cage 2 and the motion
of the rollers 6 limit each other. As a result, not only squeaking noise
caused by rubbing of the rollers against the inner and outer race surfaces
in the unloading zone is prevented but also the sound pressure level of
cage noise caused by collision of the rollers with the cage is reduced.
Furthermore, variations in vibration and noise levels of individual
bearings are suppressed.
Further, by providing the roller guide surfaces 7 of the cage 2 in portions
opposite to the linear form portion 9 except the crowning portions 8 on
the axial direction of the roller rolling surface, the rollers 6 are
hardly made unstable even in the unloading zone in which the roller motion
is limited by being guided by the cage 2, as compared with the case where
the rollers 6 are guided by portions opposite to the crowning portions 8.
Accordingly, skew, or the like, is suppressed from occurring. Accordingly,
vibration/noise of the bearing, inclusive of the cage, due to the skew, or
the like, is prevented from occurring.
As a result, the operation and effect obtained by the relations
H=5.0.times.10.sup.-3 D and A/B=0.9 and the operation and effect obtained
by provision of the roller guide surfaces 7 of the cage 2 in a portion
opposite to the linear form portion 9 except the crowning portions 8 on
the axial direction of the roller rolling surface cooperate together so
that vibration/noise of the bearing can be prevented well.
A rotation acoustic evaluation test for confirming the operation and effect
of the present invention will be described below.
The cylindrical roller bearing shown in FIG. 2 is an NU308 type cylindrical
roller bearing 100 which is used as a comparative example and which is the
same as the cylindrical roller bearing 1 shown in FIG. 1 except that
roller guide surfaces 7 of a pressed cage 101 are provided in portions
opposite to the crowning portions 8, respectively, of a roller rolling
surface. The main size of each of the cylindrical roller bearing 1 and 100
was set as follows: an outer diameter of the outer race was 90 mm; a width
in the axial direction thereof was 23 mm; an inner diameter of the inner
race was 40 mm; a roller diameter was 12 mm; and a roller length L was 12
mm.
Three samples of each of the cylindrical roller bearings 1 and 100 (six
samples in total) were prepared for the acoustic evaluation test. Noise
produced when each of the cylindrical roller bearings 1 and 100 revolved
twice (twelve times in total) was collected by a microphone and evaluated
as a sound pressure level value by a frequency analyzer (FFT).
Conditions for the test were as follows.
Test Conditions
rotational speed: 1200 rpm
lubricant: oil (ISO VG68)
radial load: 40 kgf
measurement frequency range: 0 to 10 KHz
FIG. 3 shows a result of this experiment. The horizontal axis expresses an
examination number on the two kinds of cylindrical roller bearings 1 and
100 and the vertical axis expresses an average sound pressure level in
twice measurements.
As is obvious from FIG. 3, it is found that an effect enough to prevent
vibration/noise is not obtained in the cylindrical roller bearing 100 as a
comparative example in which the roller guide surfaces 7 of the cage 101
are provided in portions opposite to the crowning portions 8,
respectively, on the axial direction of the roller rolling surface,
because the average sound pressure level is in a high range or from 67 to
73 dB and varies by about 6 dB.
This is considered as follows. In the unloading zone in which the roller
motion is limited by being guided by the cage 101, rollers are not evenly
guided by the cage 101 because of the crowning portions. Further, the
thickness of a lubricating oil film is apt to be uneven particularly in
the crowning portions 8. Accordingly, torque difference occurs between
axially opposite end portions of the roller rolling surface. Accordingly,
the rollers are made unstable easily, so that skew, or the like, occurs.
As a result, vibration/noise of the bearing is produced so that the sound
pressure level of the bearing is not reduced.
On the contrary, it is found that an effect enough to prevent
vibration/noise is obtained in the cylindrical roller bearing 1 as an
embodiment of the present invention in which the roller guide surfaces 7
of the cage 2 are provided in portions, respectively, opposite to the
linear form portion 9 except the crowning portions 8 on the axial
direction of the roller rolling surface, because the average sound
pressure level of the cylindrical roller bearing 1 is in a range of from
64 to 66 dB which is lower by about 3 dB than that of the cylindrical
roller bearing 100 which is a comparative example and varies by about 2
dB.
This is considered as follows. Since skew, or the like, With respect to the
direction of revolution of rollers guided by the cage 2 in the unloading
zone can be suppressed, the rollers can revolve around their common axis
with their stable attitudes while rotating on their own axes respectively.
As a result, the sound pressure level of the bearing is reduced.
It could be confirmed from the above description that an effect enough to
prevent vibration/noise was obtained by provision of the roller guide
surfaces 7 of the cage 2 in portions, respectively, opposite to the linear
form portion 9 except the crowning portions 8 on the axial direction of
the roller rolling surface.
Further, though not shown, the cylindrical roller bearing 1 as an
embodiment of the present invention was compared with a cylindrical roller
bearing incorporated with a conventional pressed cage as a comparative
example in which values of H and A/B do not satisfy the aforementioned
relations 1.5.times.10.sup.-3 D.ltoreq.H.ltoreq.9.0.times.10.sup.-3 D and
A/B=0.6-1.0. It was confirmed that there was obtained an effect of
reducing the average sound pressure level of the cylindrical roller
bearing 1 according to the embodiment of the present invention by about 3
dB compared with the comparative example.
A cylindrical roller bearing as another embodiment of the present invention
will be described below with reference to FIG. 4.
The cylindrical roller bearing 20 is an NU308 type cylindrical roller
bearing which is the same as the cylindrical roller bearing 1 shown in
FIG. 1 except the following points. The cylindrical roller bearing 1 is
configured so that roller dropping preventing portion 10 is provided in an
inner-diameter portion of the substantially axial center portion of the
cage 2 to thereby prevent the roller from dropping (decomposing), whereas
the cylindrical roller bearing 20 is configured so that escape portions 21
are provided in end surface portions of the rollers 6 and roller dropping
preventing projections 23 provided in a pressed cage 22 are inserted in
the escape portions 21 and that the roller guide surface 7 of the cage 22
is substantially provided in the whole region of a portion opposite to the
linear form portion 9 except the crowning portions 8 on the axial
direction of the roller rolling surf ace. Other configuration, operation
and effect of the cylindrical roller bearing 20 are the same as those of
the cylindrical roller bearing 1. In FIG. 4, parts the same as those in
FIG. 1 are referenced correspondingly so that the duplicated description
will be omitted.
FIG. 5 shows an NU308 type cylindrical roller bearing 200 used as an
example to be compared with the cylindrical roller bearing 20. The
cylindrical roller bearing 200 is the same as the cylindrical roller
bearing 20 except that roller guide surfaces 7 of a pressed cage 201 are
provided in portions, respectively, opposite to the crowning portions 8 of
the roller rolling surface.
There were prepared four samples of each of the cylindrical roller bearings
20 and 200 (eight samples in total) having main size as follows: an outer
diameter of the outer race was 90 mm; a width in the axial direction was
23 mm; an inner diameter of the inner race was 40 mm; a roller diameter
was 12 mm; and a roller length L was 12 mm. The rotation acoustic
evaluation test was carried out twice (sixteen times in total) on the
cylindrical roller bearings 20 and 200 in the aforementioned manner. As a
result, it was confirmed that an effect of reducing the average sound
pressure level by a value of from about 2 dB to about 3 dB was obtained in
the cylindrical roller bearing 20 as an embodiment of the present
invention in which the roller guide surface 7 of the cage 22 is provided
in the whole region of a portion opposite to the linear form portion 9
except the crowning portions 8 on the axial direction of the roller
rolling surface compared with the cylindrical roller bearing 200 as a
comparative example in which the roller guide surfaces 7 of the pressed
cage 201 are provided in portions, respectively, opposite to the crowning
portions 8 of the roller rolling surface.
Conditions for the test were as follows.
Test Conditions
rotational speed: 1200 rpm
lubricant: oil (ISO VG68)
radial load: 40 kgf
measurement frequency range: 0 to 10 KHz
Moreover, a cylindrical roller bearing as a further embodiment of the
present invention will be described below with reference to FIG. 6.
Referring to FIG. 6, the cylindrical roller bearing 51 is an N308 type
cylindrical roller bearing which satisfies the relations
H=5.0.times.10.sup.-3 D and A/B=0.9 when D is the diameter of a cage
circumferential surface 53 which is an inner circumferential surface of an
axial end portion of a pressed cage 52, H is the size of an annular
clearance existing between the cage circumferential surface 53 and a race
circumferential surface 55 which is an outer-diameter circumferential
surface of an inner race rib 54 opposite to the cage circumferential
surface 53, A is the axial length of the cage circumferential surface 53
and B is the axial length of the race circumferential surface 55. In the
cylindrical roller bearing 51, as a system for guiding the cage 52, a
roller guide system in which the radial displacement of the cage 52 is
limited by the engagement between each pocket and a corresponding roller
56 is used. Further, a roller guide surface 57 of the cage 52 is provided
in a portion opposite to a linear form portion 59 except crowning portions
58 on the axial direction of a roller rolling surface.
Further, a roller dropping preventing portion 60 is provided in an
inner-diameter portion of a substantially axial center portion of the cage
52 to thereby prevent the roller from dropping (decomposing). In this
embodiment, the aforementioned guide surface 57 is provided also in the
roller dropping preventing portion 60. As for the shape of the roller
rolling surface, there is used the roller rolling surface in which a
linear form portion 59 which is 70% of the roller length is left in the
lengthwise center portion of the roller 56 so that crowning portions 58
are applied to opposite ends, respectively, of the linear form portion 59.
By satisfying the relations H=5.0.times.10.sup.-3 D and A/B=0.9, the
resistance against a flow of the lubricant to pass through the annular
clearance existing between the race circumferential surface 55 and the
cage circumferential surface 53 is made sufficiently large to limit the
motion of the cage 52 to thereby limit the motion of the plurality of
rollers 56 because there is a relation that the motion of the cage 2 and
the motion of the rollers 56 limit each other. As a result, not only
squeaking noise caused by rubbing of the rollers against the inner and
outer race surfaces in the unloading zone is prevented but also the sound
pressure level of cage noise caused by collision of the rollers with the
cage is reduced. Furthermore, variations in vibration and noise levels of
individual bearings are suppressed.
Further, by providing the roller guide surfaces 57 of the cage 52 in
portions opposite to the linear form portion 59 except the crowning
portions 58 on the axial direction of the roller rolling surface, the
rollers 56 are hardly made unstable even in the unloading zone in which
the roller motion is limited by being guided by the cage 52, as compared
with the case where the rollers 56 are guided by portions opposite to the
crowning portions 58. Accordingly, skew, or the like, is suppressed from
occurring. Accordingly, vibration/noise of the bearing, inclusive of the
cage, due to the skew, or the like, is prevented from occurring.
As a result, the operation and effect obtained by the relations
H=5.0.times.10.sup.-3 D and A/B=0.9 and the operation and effect obtained
by provision of the roller guide surfaces 57 of the cage 52 in a portion
opposite to the linear form portion 59 except the crowning portions 58 on
the axial direction of the roller rolling surface cooperate together so
that vibration/noise of the bearing can be prevented well.
Although the aforementioned embodiments have shown the case where a pressed
cage is used, it is a matter of course that the pressed cage maybe
replaced by a plastic cage, a brass drilled cage, or the like, that the
material and shape of the cage and the form of the cage as to whether the
cage is of an integral type or of a separate type are not limited
specifically and that the effect for low vibration and low noise is
obtained without departing the spirit of the present invention.
Note that, even if the roller guide system of the above-mentioned
embodiment in which the radial displacement of the cage is limited by
engagement between pockets and rollers is changed to a race guide system
in which a radial displacement of the cage is limited by the race, the
motion of the rollers held by the cage and the motion of the cage can be
controlled as well, to thereby enjoy the same effects described above. The
same effects can be obtained, not only in a race guide system in which a
radial displacement of the cage is limited by the inner peripheral surface
of the ribs of the outer race, but also in a race guide system in which a
radial, displacement of the cage is limited by the outer peripheral
surface of the ribs of the inner race.
As is obvious from the above description, according to the present
invention, there is obtained an effect that not only squeaking noise
caused by rubbing of rollers with inner and outer race surfaces in the
unloading zone, cage noise caused by collision of rollers with the cage
and vibration/noise of the bearing, inclusive of the cage, caused by skew,
or the like, can be prevented well but also variations in vibration and
noise levels of individual bearings can be suppressed.
The present invention is based on Japanese Patent Application No. Hei.
10-195890, which is incorporated herein by reference.
While there has been described in connection with the preferred embodiment
of the invention, it will be obvious to those skilled in the art that
various changes and modifications may be made therein without departing
from the invention, and it is aimed, therefore, to cover in the appended
claim all such changes and modifications as fall within the true spirit
and scope of the invention.
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